Shigella

Aka: Shigella, Bacillary Dysentery, Shigellosis, Shigella sonnei, Shigella flexneri, Shigella dysenteriae, Shigella boydii

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II. Epidemiology

  1. Most common cause of bloody Diarrhea in the United States (since 2010 when surpassed E. coli 0157:H7)

III. Pathophysiology

  1. Only small inoculum required for infection
    1. Invades Small Bowel mucosa
    2. Produces enterotoxin in colon esulting in colitis
  2. Transmission
    1. Occurs via items contaminated with human feces (Hand contact, Fly infestation)
    2. Foodborne Sources (fecal-oral route)
      1. Contaminated drinking water
      2. Contaminated raw produce
      3. Foods contaminated by infected food handler
    3. Sexually Transmitted Infection (anal sex)
      1. More common among Men who have Sex with Men
  3. Four serotypes
    1. Shigella sonnei
      1. Most common Shigella species causing Infectious Diarrhea in industrialized countries
    2. Shigella flexneri
      1. Most common Shigella species causing Infectious Diarrhea in tropical and subtropical regions
      2. Growing Incidence as a Sexually Transmitted Infection in the United States
        1. Associated with anal sex and oro-anal sex, and presents with severe Diarrhea
        2. Multi-drug resistant and treatment requires susceptibility testing
        3. Associated with HIV Infection
    3. Shigella dysenteriae
      1. Less common outside of South Asia and Sub-Saharian Africa
    4. Shigella boydii
      1. Less common outside of South Asia and Sub-Saharian Africa

IV. Symptoms

  1. Onset: 4 to 7 days (as early as 1-3 days in some cases)
  2. Duration: 24 to 48 hours
  3. Diarrhea (often severe)
  4. Tenesmus
  5. Abdominal cramps
  6. Nausea and Vomiting
  7. Lassitude
  8. Bloody stool (51% of cases)
  9. Stool mucus may be seen

V. Signs

  1. Fever (58% of cases)
  2. Dehydration
  3. Lower abdominal tenderness

VI. Diagnosis: Flexible Sigmoidoscopy or Colonoscopy

  1. Hyperemic bowel wall
  2. Mural edema
  3. Purulent exudate

VII. Labs

  1. Stool microscopy
    1. Stool Mucus
    2. Fecal Leukocytes present
  2. Complete Blood Count
    1. Leukocytosis or Leukopenia
  3. Routine Stool Culture
    1. Negative only after 48 hours of Antibiotics

VIII. Management

  1. See Acute Diarrhea
  2. Treat Immunocompromised patients for 7-10 days
  3. Trimethoprim-Sulfamethoxazole (Bactrim) is no longer recommended due to Antibiotic Resistance
  4. Adults with Dysentery: first-line agents
    1. Ciprofloxacin 500 mg orally twice daily for 3 days or
    2. Levofloxacin 500-750 mg orally daily for 3 days
  5. Adults with Dysentery: alternative agents
    1. Azithromycin 500 mg daily for 3 days or
    2. Ceftriaxone 1-2 g IV daily for 3 days (in severe disease)
  6. Children with Dysentery: first-line agents
    1. Azithromycin 10 mg/kg/day daily for 3 days or
    2. Ceftriaxone 50-75 mg/kg/day for 2- 5 days (in severe disease)
  7. References
    1. (2015) Sanford Guide to Antimicrobial Therapy, IOS app accessed 5/8/2016

IX. Complications

  1. Reactive Arthritis
  2. Hemolytic Uremic Syndrome

X. Resources

  1. CDC Shigella
    1. http://www.cdc.gov/shigella/

XI. References

  1. Switaj (2015) Am Fam Physician 92(5): 358-65 [PubMed]
  2. Killackey (2016) Front Cell Infect Microbiol 6:38 +PMID: 27066460 [PubMed]

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